A well known characteristic of the immune systems of vertebrate organisms is the anamnestic response. The existence of immunologic memory has been thoroughly documented and appears to be the properties of certain lymphocytes which have undergone differentiation to become "memory cells" after contact with antigen. These memory cells have classically been ascribed to the population of long-lived, small lymphocytes although more than one population of such cells may exist. IgG, IgM and IgA are quantitatively the three major immunoglobulin in mammalian systems. Memory cells responsible for the production of IgG or IgM class antibodies in the secondary response have been described. Attempts to demonstrate immunologic memory in the secretory immune system (almost entirely restricted to IgA antibodies) have not been conclusive and attempts to demonstrate the existence of IgA memory cells have not been undertaken. As certain antigens and vaccines or natural infections stimulate almost exclusively a local IgA response, particularly when administered locally, it would be of great importance to clinical and basic immunology to determine whether immunologic memory is present in the secretory immune system. This proposal investigates this issue using the system of adoptive transfer of immunologically competent cells from immunized donor rats to irradiated syngeneic recipients.